1. Field of the Invention
The present invention relates to an image capturing device having a TOF camera and a CCD camera, an occlusion region searching method, and a program.
2. Description of the Related Art
In the field of computer vision, particularly robot vision, the use of three-dimensional information is very important as described in a document by D. A. Forsyth, J. Ponce, “A Modern Approach”, Computer Vision, Prentice Hall, 2002. For example, it is essential for autonomous robots, which recognize objects, make decisions, and perform tasks in real space, to have a function to perform three-dimensional recognition in real time in the environment in which they are present, such as shapes and motions of objects around them, just like human beings.
In recent years, the progress of three-dimensional measurement technology is remarkable, and there have been proposed various techniques related to three-dimensional measurement technology. The proposed techniques are generally classified into techniques which employ passive sensors and techniques which employ active sensors. The former class of techniques is referred to as a multi-view measurement technique typified by a stereographic technique involving a plurality of CCD cameras. Particularly, a baseline stereographic technique involving two cameras arranged parallel to each other is widely used in the art at present. However, it is generally not easy to restore three-dimensional information from two-dimensional information which is dimensionally-reduced. In particular, the restoration of three-dimensional information from multi-view image information needs to perform a task of searching for corresponding points between images and finds it difficult to fully avoid a large reduction in accuracy due to wrong corresponding points. Furthermore, it is impossible in principle to measure the distance between objects of reduced texture. It is also computationally expensive to search for corresponding points.
The latter class of techniques is advantageous in that active sensors such as laser range finders are less susceptible to illumination and are capable of measuring distances at higher speeds with higher accuracy than stereographic cameras. However, three-dimensional laser range finders are not suitable for use in applications such as home robots because they are large by themselves and very expensive. A process of obtaining highly accurate three-dimensional information by actuating a two-dimensional laser range finder with motors is often used for environmental mapping in mobile robots. However, since the two-dimensional laser range finder is moved by motors, the robot needs to keep still each time the two-dimensional laser range finder performs a scanning process. One active sensor which has been proposed to solve the above problem is an infrared TOF (Time Of Flight) camera as disclosed in a document by T. Oggier, F. Lustenberger and N. Blanc, “Miniature 3D TOF Camera for Real-Time Imaging”, in Proc. of Perception and Interactive Technologies, 2006. pp. 212-216, June 2006. Such an infrared TOF camera is capable of acquiring three-dimensional information at a rate of about 30 fps according to TOF measurements using a modulated near-infrared radiation. Although the infrared TOF camera is greatly lower in accuracy than the laser range finder, it is much higher in accuracy than baseline stereographic cameras, and the infrared TOF camera is considered to be useful in many applications. Since the infrared TOF camera is relatively small, it can easily be installed on mobile robots for home use. One general problem of an active sensor is that it cannot acquire color information of acquired coordinates.